Camshaft adjusters of the aforementioned type serve to make possible valve control which is variable or as optimized as possible. They offer the possibility of adjusting the phase angle of the valve control continuously and in a controlled manner. For this, a camshaft adjuster is connected to the respective camshaft in a manner that it is fixed against turning and force-locking.
Depending on the presetting of monitoring and control electronics, a turning motion is transmitted to the camshaft and thereby a respective desired setting of the camshaft relative to the crankshaft of the internal combustion engine is preset.
Customary camshaft adjusters are usually driven hydraulically. The oil pressure needed to adjust the camshaft is obtained from the lubricant oil circuit associated with the internal combustion engine in question. In so doing, there is the problem that, precisely in the motor start phase critical for exhaust gas, the camshaft is still not in the desired position relative to the crankshaft.
The current generation of camshaft adjusters which change the angular position of the camshaft continuously is represented by systems which are constructed according to the oscillating motor principle.
The advantages of systems of this type are the continuous adjustment of the camshaft and the compact and economical mode of construction. An economical process for the production of camshaft adjusters is the sintering process, which is also suitable for mass production.
The aforementioned systems are provided, via the oil pump, with pressure oil from the lubricant oil circuit, where, during so-called “hot idling,” these systems also have to function at oil temperatures of 150° C. and pressures of <0.5 bar at the idling speed of the motor. Thermal effects which can occur, due to the temperatures of at most 150° C. reached in the operation of the motor, must be taken into account in the design of the component size and tolerances.
From DE 100 62 981 A1 a camshaft adjustment device operating according to the so-called vane-cell principle is known. A drive wheel comprises a cavity formed by a peripheral wall and two side walls, where in said cavity at least one hydraulic working space is formed by at least two bounding walls. A vane extending in the hydraulic working space divides the hydraulic working space into two hydraulic pressure chambers. Gaps between a head of a pressurizing medium distributor and an opening of one side wall of the drive wheel and/or between the lateral surface and an opening of the other side wall of the drive wheel are sealed, by wear-resistant sealing means, against leaks of pressurizing medium.
DE 198 08 619 A1 describes a locking device for a vane-cell adjustment device. There a mechanical coupling between a vane wheel and a drive wheel can be produced by at least one vane of the vane wheel, where that vane is movable in the axial direction and is formed as a vane wheel pivoting element and at the same time as a locking element.
From DE 100 20 120 A1 a vane-cell adjustment device is known in which, between a pivotable vane wheel and a drive wheel, radial gaps are provided which are formed to be enlarged, while the sealing elements are formed as sealing strips which can be pivoted in both turning directions of the pivotable vane wheel and which can be pivoted with the pressure of the hydraulic pressurizing medium against the respective counterface on the drive wheel or on the pivotable vane wheel.
In the vane-cell adjustment device of DE 101 09 837 A1 a drive unit is mounted so that it can be pivoted over several radial mounting points on a drive unit, where at least the surface of the individual radial mounting segments of the drive unit and the opposing radial mounting segments of the drive unit as well as optionally also the axial contact surfaces between the drive unit and the drive unit are formed with a friction-reducing coating.
From the Patent Abstracts of Japan JP 11013431 a vane-cell adjustment device is known in which, to achieve a compact structure, transmission of the turning is accomplished by means of three pins which engage in corresponding elongated holes in the housing of the vane-cell adjustment device.
It is problematic in camshaft adjusters of this type that, to avoid greater internal leakage in the pressure chambers, narrow tolerances must be adhered to, which can only be adhered to with undesirable expenditure, in particular if components of this type are produced with sintering technology. In production using sintering technology these tolerances can thus only be achieved by corresponding complicated mechanical processing, or via clearly reduced number of pieces. Furthermore, in the case of most camshaft adjusters, locking mechanisms or restoring springs must be built in order to guarantee function during so-called “hot idling.”